A study of more than 11 000 children followed for over six years has found that young children with sleep-disordered breathing are prone to developing behavioural difficulties such as hyperactivity and aggressiveness, as well as emotional symptoms and difficulty with peer relationships, according to researchers at Albert Einstein College of Medicine of Yeshiva University.
Their study, the largest and most comprehensive of its kind, published online in the Journal Pediatrics.
"This is the strongest evidence to date that snoring, mouth breathing, and apnoea [abnormally long pauses in breathing during sleep can have serious behavioural and social-emotional consequences for children," said study leader Karen Bonuck, Ph.D., professor of family and social medicine and of obstetrics & gynaecology and women's health at Einstein.
"Parents and paediatricians alike should be paying closer attention to sleep-disordered breathing in young children, perhaps as early as the first year of life."
Sleep-disordered breathing (SDB) is a general term for breathing difficulties that occur during sleep. Its hallmarks are snoring (which is usually accompanied by mouth breathing) and sleep apnoea. SDB reportedly peaks from two to six years of age, but also occurs in younger children.
About one in 10 children snore regularly and 2% to 4% have sleep apnoea, according to the American Academy of Otolaryngology–Health and Neck Surgery (AAO-HNS). Common causes of SDB are enlarged tonsils or adenoids.
"Until now, we really didn't have strong evidence that SDB actually preceded problematic behaviour such as hyperactivity," said Ronald D. Chervin, M.D., M.S., a co-author of the study and professor of sleep medicine and of neurology at the University of Michigan.
"Previous studies suggesting a possible connection between SDB symptoms and subsequent behavioural problems weren't definitive, since they included only small numbers of patients, short follow-ups of a single SDB symptom, or limited control of variables such as low birth weight that could skew the results.
But this study shows clearly that SDB symptoms do precede behavioural problems and strongly suggests that SDB symptoms are causing those problems."
The new study analysed the combined effects of snoring, apnoea and mouth-breathing patterns on the behaviour of children enrolled in the Avon Longitudinal Study of Parents and Children, a project based in the United Kingdom.
Parents were asked to fill out questionnaires about their children's SDB symptoms at various intervals, from six to 69 months of age. (Studies of similar questionnaires have shown that parents do a good job of assessing kids' SDB: their evaluations compare well with data from carefully controlled overnight sleep studies, Dr Bonuck reports.) .
When their children were approximately four and seven years old, parents filled out the Strengths and Difficulties Questionnaire (SDQ), which is widely used to assess behaviour. The SDQ has scales for assessing a child's inattention/hyperactivity, emotional symptoms (anxiety and depression), peer problems, conduct problems (aggressiveness and rule-breaking), and prosocial behaviour (sharing, helpfulness, etc.).
The researchers controlled for 15 potential confounding variables, including socioeconomic status, maternal smoking during the first trimester of pregnancy, and low birthweight.
"We found that children with sleep-disordered breathing were from 40 to 100% more likely to develop neurobehavioral problems by age seven, compared with children without breathing problems," said Dr Bonuck. "The biggest increase was in hyperactivity, but we saw significant increases across all five behavioural measures."
SDB may affect brain
Children whose symptoms peaked early—at six or 18 months—were 40% and 50% more likely, respectively, to experience behavioural problems at age seven compared with normally-breathing children. Children with the most serious behavioural problems were those with SDB symptoms that persisted throughout the evaluation period and became most severe at 30 months.
Researchers believe that SDB could cause behavioural problems by affecting the brain in several ways: decreasing oxygen levels and increasing carbon dioxide levels in the prefrontal cortex; interrupting the restorative processes of sleep; and disrupting the balance of various cellular and chemical systems.
Behavioural problems resulting from these adverse effects on the brain include impairments in executive functioning (i.e., being able to to pay attention, plan ahead, and organise), the ability to suppress behaviour, and the ability to self-regulate emotion and arousal.
"Although snoring and apnea are relatively common in children, paediatricians and family physicians do not routinely check for sleep-disordered breathing," said Dr Bonuck. "In many cases, the doctor will simply ask parents, 'How is your child sleeping?' Instead, physicians need to specifically ask parents whether their children are experiencing one or more of the symptoms—snoring, mouth breathing or apnea—of SDB."
"As for parents," said Dr Bonuck, "if they suspect that their child is showing symptoms of SDB, they should ask their paediatrician or family physician if their child needs to be evaluated by an otolaryngologist (ear, nose and throat physician) or sleep specialist."
According to the AAO-HNS, surgery is the first-line treatment for severe paediatric SDB in cases where the tonsils and adenoids are enlarged. Another option is weight loss for overweight or obese children.
(EurekAlert, March 2012)